Make sure you are using the correct bulk sell yours tool. Use the Bulk Upload tool for adding new listings, and the Bulk Update tool for changing or deleting existing listings.

Check your selling price. Prices shouldn't be more than 10% above the recommended retail price. Lines that exceed this amount are skipped (these are unlikely to sell anyway, so best to revise your price down).

Check that the item is in Fishpond's catalogue. If it's not, you can add it using the Add a Product tool and run the line again.